A transient technique using the temporal analysis of products reactor system was used to determine the intracrystalline diffusion coefficients of isobutane and 2-methylpentane in a H-ZSM-5 zeolite sample at between 423 and 598K. A mathematical model was set up which described the transport phenomena occurring in the transient experiment. The intracrystalline diffusion coefficient of isobutene at 423K was deduced to be 5 x 10-12m2/s, with an activation energy of 25kJ/mol. The intracrystalline diffusion coefficient of 2-methylpentane at 423K was deduced to be 1 x 10-12m2/s, with an activation energy of 24kJ/mol. The features of this model were then explored by model simulation. The method and the underlying model were successfully validated by fitting experimental data, deriving intracrystalline diffusion coefficients by parameter estimation, and comparing them with published values obtained by independent methods.

Determination of the Intracrystalline Diffusion Coefficients of Alkanes in H-ZSM-5 Zeolite by a Transient Technique using the Temporal-Analysis-of-Products (TAP) Reactor. O.P.Keipert, M.Baerns: Chemical Engineering Science, 1998, 53[20], 3623-34